When two individuals engage in a contest of strength, seemingly innocuous procedures on the part of one can lead to the defeat of the other. Two such procedures are "X-ing" and "gentle resistance." To X, one contestant draws his/her hand rapidly across the body axis of the other twice at close range but without touching so as to form an X centered over the lower end of the sternum. This is done just before the contest begins. To apply gentle resistance, one contestant relaxes the arm used for the competition and while the contest is in progress imagines that the arm is an open conduit through which he/she draws off the other contestant's "aggressive energy." An individual can reliably defeat "stronger" opponents using these techniques after only a few minutes training. Preliminary measurements of the forces applied during control (no X-ing) trials and trials preceded by X-ing suggest that the Xed contestants (the subjects) were displaced at lower forces after X-ing than they could resist during the controls, even though the force did not start earlier or rise more rapidly after X-ing. Similar results have been obtained during gentle resistance. Whether or not the subjects knew that X-ing or gentle resistance had occurred made little difference. The aim of the experiments proposed herein is to determine whether the subject is changed by the X-ing and gentle resistance procedures, as our preliminary data suggest, or whether the changes are confined to the contestant who applies these procedures (the experimenter). To this end, we propose (1) to extend the range and precision of the measurements made after X-ing and during gentle resistance; (2) to study the effect of X-ing by a third party so that neither the subject nor the experimenter knows that X-ing has occurred; (3) to mechanically decouple the subject and experimenter during control, X-ing and gentle resistance trials and measure the force generated by each to look for decreases in force production by the subject and to test the possibility that a so far undetected increase in motor output by the experimenter causes the subject to be displaced; and (4) to deliver defined force perturbations to the experimenter and subject during control, X-ing and gentle resistance trials to more precisely define the ability of each to resist displacement (i.e., measure their joint stiffness). If the experiments indicate that the subjects are changed by X-ing and gentle resistance so that they can resist displacement less well, this would be unexpected since it is already clear that the effects do not depend on suggestion or cuing of the subjects. If the experiments indicate that only the experimenter is changed, it is not clear at present how he/she can bring about the subject's defeat without causing the force against the subject to rise more rapidly or to higher levels than in the control trials. Thus, regardless of their outcome, the experiments should provide interesting insights into motor function.